Organopolysiloxanes that contain a radically polymerizable group (e.g., acryloxy or methacryloxy) in each molecule are known. Known in this regard are, for example, straight-chain polydimethylsiloxanes in which only a single terminal is endblocked by methacryloxypropyl and the following polydimethylsiloxane having a single branch point in the molecule ##STR2##
are described in Japanese Laid Open (Kokai or Unexamined) Patent Application Numbers Hei 7-196975 (196,975/1995), Hei 1-319518 (319,518/1989), and Hei 1-254719 (254,719/1989)). The use of these straight-chain organopolysiloxanes and branched organopolysiloxanes as co-monomers in the synthesis of various organic resins provides copolymers that have a low surface tension and an excellent surface lubricity. These copolymers, however, have poor compatiblilty with non-silicone-type organic resins.
In response to this problem, the present inventors have already disclosed a carbosiloxane dendrimer in the form of a multibranched siloxane-silalkylene copolymer that contains in each molecule one radically polymerizable group and at least 2 branch points (Japanese Laid Open (Kokai or Unexamined) Patent Application Numbers Hei 11-1485 (1,485/1999) and Hei 11-1530 (1,530/1999)). This carbosiloxane dendrimer can, for example, be reacted with other radically polymerizable monomers to produce a variety of graft copolymers bearing pendant dendrimer structures. However, the radically polymerizablc group and the dendrimer structure in this dendrimer are either directly bonded to each other or are bonded to each other across a lower alkylene group such as the propylene group. As a consequence, when this dendrimer is polymerized by itself or at high concentrations with other organic monomers, the reactivity is lowered by steric hindrance and the reaction does not proceed to completion.